I have merged my branch archer-swagiaal-using-directive into Keiths'
branch archer-keiths-expr-cumulative, and resolved conflicts. If Keith
is done with archer-keiths-expr-cumulative, it is ready to go.

Have you run the branch through the test suite before your commit? I
updated my copy of the branch today and picked up your using directive
changes, and now I'm seeing a bunch of new failures (38 new failures) --
all seem to be failing the same way.